According the graphic render that seems to be very poor, a new picture using actor messages to change the default texture of blocks.
After several graphic tests, I strongly recommand the use of custom cubes models, due to the texture render style of the ShapeCube model featured by Blizzard.
Then... It's very easy to make custom models for this kind of project... Create a cube, set the same material for each face, then import. All kinds of cubes could be made in game with the use of custom textures (with Actor message "Select Texture By Id").
I'm working on a "DataAchievement" library (Achievement library using the Data Editor as the base of development) for the moment. CUBE³ could be a later project for me, but not sure at all.